1. Field of the Invention
The invention relates to a high-pressure gas discharge lamp comprising a quartz glass lamp vessel which is closed in a gastight manner, with a space which is enclosed by a wall and in which a pair of electrodes is arranged, an outer surface of said wall extending between the pair of electrodes and a filling provided in the space and comprising a rare gas and halides of tin and indium.
2. Discussion of the Prior Arts
Such a high-pressure gas discharge lamp is known from the patent document DE 24 55 277 (=U.S. Pat. No. 4,001,626). The lamp generates light of a comparatively high intensity during operation because tin halide is present in the filling. The presence of indium halide in the filling gives the emitted light a color point and a color temperature which approximate an envisaged color point and an envisaged color temperature to a certain extent. The lamp vessel is made of quartz glass, i.e. glass having an SiO2 content of at least 95% by weight. A disadvantage of the known lamp is an unacceptably fast corrosion and/or crystallization of the wall of the lamp vessel. This corrosion and/or crystallization is due partly to an attack by the filling. The result is that the lamp has a comparatively bad lumen maintenance, and scattering of light will occur, so that focusing of the light is comparatively bad. The corrosion and/or crystallization leads to additional disadvantages involving a comparatively high risk of a comparatively short life of the lamp and/or inflation, i.e. an increase in the volume enclosed by the lamp vessel wall.
The same patent document also describes the filling, to which lithium chloride or sodium chloride has been added. The emitted light of a lamp whose filling has such an additive has a color point and a color temperature which approximate the envisaged color point and the envisaged color temperature comparatively closely. Such a lamp, however, suffers the disadvantage of a fast corrosion and/or crystallization of the lamp vessel wall even more strongly.